package org.learn.a1_100_leet_code.a_2;

/**
 * You are given two non-empty linked lists representing two non-negative integers.
 * The digits are stored in reverse order, and each of their nodes contains a single digit.
 * Add the two numbers and return the sum as a linked list.
 * <p>
 * You may assume the two numbers do not contain any leading zero, except the number 0 itself.
 * <p>
 * Example 1:
 * Input: l1 = [2,4,3], l2 = [5,6,4]
 * Output: [7,0,8]
 * Explanation: 342 + 465 = 807.
 * Example 2:
 * <p>
 * Input: l1 = [0], l2 = [0]
 * Output: [0]
 * Example 3:
 * <p>
 * Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
 * Output: [8,9,9,9,0,0,0,1]
 * <p>
 * Constraints:
 * <p>
 * The number of nodes in each linked list is in the range [1, 100].
 * 0 <= Node.val <= 9
 * It is guaranteed that the list represents a number that does not have leading zeros.
 */
public class AddToNumbers {

    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode head = null, tail = null;
        int carry = 0;
        while (l1 != null || l2 != null) {
            int n1 = l1 != null ? l1.value : 0;
            int n2 = l2 != null ? l2.value : 0;
            int sum = n1 + n2 + carry;
            if (head == null) {
                head = tail = new ListNode(sum % 10);
            } else {
                tail.nextNode = new ListNode(sum % 10);
                tail = tail.nextNode;
            }
            carry = sum / 10;
            if (l1 != null) {
                l1 = l1.nextNode;
            }
            if (l2 != null) {
                l2 = l2.nextNode;
            }
        }
        if (carry > 0) {
            tail.nextNode = new ListNode(carry);
        }
        return head;
    }

}

